Lap



Nov. 23, 1943.

M. A. LAMBRIX 2,335,125

LAP

Filed April 5, 1941 INVENTQR MauriceA-Lambrix ATTORNEYS Patented Nov. 23, 1943 LAP Maurice A. Lambrix, Cleveland, Ohio, assignor to Gear Processing, Inc., Cleveland, hio,a corporation of Ohio Application April 3, 1941, Serial No. 386,697

4 Claims.

This invention relates to laps for trueing gears by the method of Copland Reissue Patent 17,884, granted November 25, 1930, in which the gear and lap are formed to interfit, one being in the form of an external gear and the other an internal gear, and both of substantially pitch diameter and tooth spacing, so that one may be reciprocated within the other to true the gear teeth of the gear by abrasive action.

It has been found that the hardening heat treatment to which gears are subjected tends to distort certain types of gears appreciably out of round. This distortion makes necessary a greater amount of grinding upon the faces of teeth adjacent the long and short axes of the distorted gear in order to reestablish uniformity of tooth spacing and tooth contour. Also the lapping of a considerable number of gears which have similar errors in contour and spacing tends to wear the lap teeth unevenly and makes it more difiicult to maintain the correct form and spacing of the lap tooth surfaces.

The present invention is a lap for use in a preliminary trueing operation by which a gear distorted out of round may be first ground adjacent the ends of its longer axis to restore the gear to more nearly round form prior to the final lapping operation, thereby reducing the wear on the finishing lap and making it possible to maintain greater accuracy in the finished gears.

With the above and other objects in view the invention may be said to comprise the lap as illustrated in the accompanying drawing hereinafter described and particularly set forth in the appended claims, together with such variations and modifications thereof as will be apparent to those skilled in the art to which the invention pertains.

Reference should be made to the accompanying drawing forming a part of this specification, in which:

Figure 1 is a top plan view showing a lap embodying the invention and a gear interfitted with the lap for axial reciprocation with respect thereto;

Fig. 2 is a section taken on the line 2-2 in Fig. 1;

Fig. 3 is a plan View of the lap; and

Fig. 4 is a diagrammatic plan view of the gear showing the elliptical distortion, a portion only of the teeth being shown, the distortion being exaggerated for the purposes of illustration.

Referring to the accompanying drawing, the lap of the present invention is in the form of an annulus l which has opposite quadrants 2 and 3 formed with internal teeth 4, and intermediate quadrants 5 and 6 which are recessed throughout their length to a depth at least equal to the height of the internal teeth 4. The teeth 4 are teeth of an internal gear of the same pitch diameter and spacing as that of the gear 8 to be lapped, so that the gear 8 may be inserted into the lap with teeth in opposite quadrants thereof disposed in the spaces between the teeth 4 of the lap.

The lap is herein illustrated as having the form of an internal gear. It is to be understood, however, that the process is equally applicable to the finishing of external or internal gears, laps for internal gears being in the form of a complemental external gear, as explained in the Copland patent above referred to.

In Figs. 1 and 2 of the drawing the lap l is shown mounted upon a base 9, being clamped to the base by means of a ring I9 which rests upon a spacer II and which is secured in place by means of bolts I2. The gear 8 is secured by suitable means, such as bolts l3, to a spindle M which may be mounted for reciprocation to reciprocate the gear within the lap. The lap of the present invention differs from laps heretofore used in that the teeth of the lap are cut away in opposite quadrants so that the grinding action is confined to teeth in opposite quadrants of the gear. The gear 8 is inserted into the lap I to engage the teeth which are at the ends of the longer axis of the distorted gear with the lap teeth 4. By reciprocating the gear in engagement with the lap, the teeth of the gear engaged with the teeth 4 of the lap are ground, while the teeth of the gear positioned in the recessed quadrants of the lap are not ground. During the lapping operation the gear may be indexed from time to time to distribute the wear more evenly upon the lap teeth. In lapping gears by the Copland process the gear and lap are so mounted that one is free to move radially in any direction with respect to the axis of the other so that when the gear is positioned in the lap and a turning force is applied to the gear, the gear automatically centers itself with respect to the lap. By providing teeth in opposite quadrants of the lap, the grinding action is localized but the position of the gear in the lap is controlled in the same way as in a full tooth lap.

In Fig. 4 of the drawing the pitch circle of the gear prior to heat treatment is the circle indicated by the diameter A. The gear periphery is distorted by the heat treatment to elliptical form with a diameter B slightly shorter than the diameter A and a diameter C slightly longer than the diameter A.

After the preliminary grinding operation in the lap I, the gear is preferably finished in a lap having a full set of teeth. Since the operation of the lap I is in effect a roughing operation, it is not so important that the teeth of the lap I be maintained in exactly correct form and the lap I may be use'd'for a longer period of time than would be practicable for a full" tooth finishing lap. Also, the preliminary grinding operation in the lap l makes it possible to finish the gear in a much shorter time in the full tooth" finishing lap, and since the elliptical distortion is to a large extent corrected before the gear is placed in the finishing lap, there is less tendency to wear the teeth of the finishing lap to an incorrect form.

It is to be understood that variations and modifications of the specific devices herein shown and described for purposes of illustration, may be made without departing from the spirit of the invention.- 4

What I claim is:

1-. A unitary roughing lap for reducing the elongation of gears which have been distorted out of round by ahardening heat treatment said lap havingteeth corresponding to the teeth of a gear of substantially the same pitch diameter and tooth spacing as the gear to be lapped and ot a formcomplemental to that of the gear whereby the gear and lap fit tog-ether one Within the other for relative axial sliding movement, said lap having two diametrically opposite: segments provided with teeth adapted to interfit with the teeth on diametrically opposite portions of the gear and integral segmental portions intermediate the toothed segments which are reternal teeth formed to substantially the same pitch diameter as the teeth of the gear and having substantially the same spacing whereby the gear may be placed within the lap with teeth thereof in sliding engagement with teeth of the lap, said lap having two diametrically opposite segments provided with teeth adapted to interfit with the teeth on diametrically opposite portions of the: gear and connecting portions intermediate the two toothed segments and integral therewith which have an internal diameter greater than the external diameter of the gear whereby the gear engages only with the two opposed toothed segments of the lap.-

3. A unitary roughing lap for reducing the elongation of gears which have been distorted out of round, comprising a member of circular form having teeth of a gear in opposite quadrants thereof and having its intermediate quadrants recessed throughout their length to a depth at least equal to the depth of said teeth.

4. A unitary roughing lap for reducing the elongation of gears which have been distorted out of round, comprising an annulus having teeth of an internal gear in. opposite quadrants thereof and having its intermediate quadrants recessed throughout their length to a depth at least equal to the depth of said teeth,

MAURICE A. LAIVIBRIX. 

